Adding pages to the sidebar is easy.
1. Head on over to your administration area.
2. Click on "Page Management".
3. Click on "Create a New Page".
4. Enter a label for your new page.
The label is what will appear in the sidebar.
5. Select the type of page you'd like to create, and submit.
The default page type is an HTML content page where you can submit just about anything.
Alternatively, you can embed a PDF, website, or image without having to deal with <iframes> or <objects>.
6. Edit the content of the page.
(This is a screenshot for a page with an embedded website. Other page types will look a bit different.)
7. Save the page.
Don't forget to save your updates, to make them live!